PROJECT SUMMARY The proposed study is a longitudinal cohort study of 100 to 110 preterm infants born between 24 and 28 weeks gestation. It is designed to explore the contribution of delayed or aberrant ventilatory control to the need for continued respiratory support at 8 to 12 weeks of age.. Infants will be categorized according to why they seem to need respiratory support, using challenge studies. Ventilatory control will be further investigated using novel techniques for calculation of loop gain of the respiratory system and to explore the links between abnormalities seen by magnetic resonance imaging (MRI) ands aberrant ventilatory control. The proposed studies are also designed to help clarify the indications for airflow support, supplemental oxygen therapy and a ventilatory stimulant ? caffeine ? as these infants grow and mature.